defmodule Mix.Tasks.Phia.Design.Export do
  @moduledoc """
  Export a saved PhiaUI design to HEEx or LiveView source files.

  Takes a `.phia.json` file (created by `mix phia.design` or the MCP server)
  and generates production-ready Phoenix code.

  ## Usage

      mix phia.design.export my_design.phia.json
      mix phia.design.export my_design.phia.json --format liveview --output lib/my_app_web/live/page_live.ex
      mix phia.design.export my_design.phia.json --format heex --output lib/my_app_web/templates/page.html.heex

  ## Options

  - `--format` (`-f`) — Output format: `heex` (default) or `liveview`
  - `--output` (`-o`) — Output file path (prints to stdout if omitted)
  - `--module` (`-m`) — Module name for LiveView format (default: `MyAppWeb.DesignedLive`)
  - `--web-module` — Phoenix web module (default: `MyAppWeb`)

  ## Examples

      # Quick preview — print HEEx to terminal
      mix phia.design.export priv/phiaui_design/projects/dashboard.phia.json

      # Generate a LiveView module
      mix phia.design.export dashboard.phia.json \\
        -f liveview \\
        -o lib/my_app_web/live/dashboard_live.ex \\
        -m MyAppWeb.DashboardLive

  ## Related Tasks

  - `mix phia.design` — visual editor
  - `mix phia.design.mcp` — MCP server for Claude Code
  - `mix phia.design.analyze` — analyze a design file
  """

  @shortdoc "Export a .phia.json design to HEEx or LiveView code"

  use Mix.Task

  alias PhiaUiDesign.Canvas.Persistence
  alias PhiaUiDesign.Codegen.{HeexEmitter, LiveviewEmitter}

  @impl Mix.Task
  def run(args) do
    {opts, positional, _} =
      OptionParser.parse(args,
        strict: [
          format: :string,
          output: :string,
          module: :string,
          web_module: :string,
          help: :boolean
        ],
        aliases: [f: :format, o: :output, m: :module, h: :help]
      )

    if opts[:help] || positional == [] do
      Mix.shell().info(@moduledoc)
      return_or_halt()
    end

    Application.ensure_all_started(:phia_ui)

    [input_path | _] = positional
    format = Keyword.get(opts, :format, "heex")
    output_path = opts[:output]
    module_name = Keyword.get(opts, :module, "MyAppWeb.DesignedLive")
    web_module = Keyword.get(opts, :web_module, "MyAppWeb")

    unless File.exists?(input_path) do
      Mix.raise("File not found: #{input_path}")
    end

    case Persistence.load(input_path) do
      {:ok, scene, metadata} ->
        Mix.shell().info("Loaded design '#{metadata.name}' from #{input_path}")

        code =
          case format do
            "liveview" ->
              LiveviewEmitter.emit(scene, module_name, web_module: web_module)

            _ ->
              HeexEmitter.emit(scene)
          end

        if output_path do
          File.mkdir_p!(Path.dirname(output_path))
          File.write!(output_path, code)
          Mix.shell().info("Exported #{format} to #{output_path}")
        else
          Mix.shell().info(code)
        end

      {:error, reason} ->
        Mix.raise("Failed to load #{input_path}: #{inspect(reason)}")
    end
  end

  defp return_or_halt do
    if function_exported?(System, :halt, 1), do: System.halt(0)
  end
end